The invention relates to a semiconductor device having at least one field effect transistor integrated monolithically on a substrate with a diode, this transistor having ohmic source and drain contacts provided on a first n-type semiconductor layer formed at the surface of the substrate, while a gate electrode forming a rectifying junction with said first semiconductor layer is arranged between the source and drain contacts, said diode having a Schottky contact provided on a second n-type semiconductor layer also formed at the surface of the substrate.
The invention is used in the manufacture of the decoupling capacitances arranged between the d.c. supply and ground, for example in integrated circuits of gallium arsenide.
A Schottky diode forming a capacitive element integrated monolithically with a field effect transistor of gallium arsenide is known from the prior art, i.e. from published Japanese Patent Application 59-112 645 (A) of 1984. This application describes a diode formed by a first n-type layer provided on a semi-insulating substrate of gallium arsenide, this layer carrying a Schottky contact and being adjacent to a first n.sup.30 -type layer. The transistor monolithically integrated with this diode comprises a Schottky gate contact formed at the surface of a second n-type layer adjoining on the one hand the first n.sup.30 -type layer and on the other hand a second n.sup.30 -type layer carrying the ohmic drain contact.
When manufactured in this manner, this structure would have to form the combination of a Schottky gate field effect transistor and diode serving as a capacitance, whose electrode is common to the source of the transistor. It should be noted that the contact common to the source and the cathode is not obtained by forming an ohmic layer at the surface of the first n-type layer.
In order to avoid switching noise being generated in the integrated circuits, it is absolutely necessary to provide a decoupling capacitance between the d.c. supply of these circuits and a reference electrode such as ground. If the integrated circuit has slow transitions (&lt;50 ps), this capacitance can be arranged externally to the circuit and be connected to the d.c. supply and to ground through thin wires. However, if the integrated circuit has rapid transitions (&gt;50 ps), the impedance of the flexible connection wires, which is then very high, has an unfavorable influence on the efficiency of the decoupling by an external capacitance thus connected.
Therefore, especially for the use aimed at in integrated circuits on semiconductors of the III-V group, which permit extremely rapid transitions, the decoupling capacitance of the d.c. supply has to be integrated with the microcircuit in order to avoid the use of the flexible connection wires.